Typewriting machine



Nov. 2, 1937. w. A. DOBSON TYPEWRITING MACHINE Filed Nov; 22, 1932 ATTORNEY/ Patented Nov. 2, 1937 'TYPEWRITING MACHINE 7 William A. Dobson, Wethersfield, Conn, assignor to Underwood Elliott Fisher Company, New York, N. Y., a c orporation of Delaware Application November 22, 1932, Serial No. 643,811

6 Claims.

This invention relates to means for securing quiet operation of typewriting machines.

In machines of the Underwood type, in which the type-bars swing up and back against a' platen,

the distance traveled by the heavy type-end of the bar is very great, necessitating high velocity, which becomes higher as the platen is approached, so that the noise of type-bar concussions is highly objectionable.

10' The type strikes against a work-sheet which is wrapped around a platen that is mounted upon a carriage, and the carriage must be stepped quickly between the rapid type-impressions; To permit speed, the carriage and platen have been made relatively light, and the swift striking of the heavy type-bar against the light platen has proven to be a serious drawback.

It has been sought to overcome this objection by enclosing the typewriting machine in a soundproof cabinet, but this has proven to be expensive.

Another means of minimizing the noise of operation has been to mount the types upon complicated movement-trains,- which press the type against the paper, instead of causing it to strike,

but this also has proven to be expensive.

It is sought by the present invention to typewrite so quietly that the machine can be'successiully used in oflices where the usual typewriter noise would be unbearable, and to do so go'practically and inexpensively and without detracting from the simplicity of the machine. The invention is shown embodied in an Underwood portable typewriter, whose low cost is not appreciably enhanced by the present invention.

35' The organization of elements herein disclosed produces a successful machine of this class, which is being manufactured in large numbers for satisfied users.

The problem to which this invention is ad- 40 dressed, involves interdependent conditions, the

chief of which is the necessity for speeding the type after it has once been started on its way' to the platen. The start of the type is slowed,

so as to render the key-touch easy; but the re- 45 sultant loss of time has to be made up at a later stage of the type-bar stroke, so that the key will not have to dip too far. Moreover, the momentum of the operators hand has to be absorbed to a great extent, the momentum being used in 50 increasing the speed of the type-bar, so that the finger may not be jarred at the conclusion of the down stroke of the key.

This particular one of the interdependent conditions, according to the present invention, is

55 largely overcome by suddenly reducing the speed tice to ofler a machine that is noticeably-more of'the type-bar, beginning at a pointnear the platen, there being providedfor this purposefan elastic padof high-grade rubber-packing, which is encountered by the type-bar when it is of an inch from the platen. Said packing'yields, but is 5 resistant to the action of the type-bar, and slows the same to a degree at which,runder usualcon ditions, it would deliver an under-strength impression upon the work-sheet, while the noise of the type-blow would still be considerably above 10 the maximum of auricular tolerance. g

7 Another of the interdependent unfavorable conditions is the resonance of the platen. It s lightness causes it to augment the noise of concussion, even when the type-banbeing cushioned as 15 7 aforesaid, makes a weak impression'as explainedg' This invention at this stage of the'difiiculty; produces a two-fold result, name1y,'it reduces the sound to bearable limits, and also insures that the Weak blow of the type shall produce a bright and 0 sharp impression upon the work-shet.- 1 To gain this double result in the described reorganization, the platen is madeupon a Weighted base consisting of a length of heavy-irongaspipe, upon which is vulcanized a cylinder of 25 heavily weighted soft rubber; and this is jacketed r by wear-resisting rubber of medium hardness, that is, considerably softer than isusually-em ployed for manifolding purposes. The great weight of the platen, due partly to its heavymetal core, and'partly tothe heavily weighted though sof rubber cylinder thereon (covered by j the jacket), is sufiicient to enable the light typeblow to make .an excellent, well-inked, clear impression upon the work-sheetfwhile the same organization reduces *the -noise of the already.- subdued blow to a point whichis within the limit 7 of tolerance to the ear. Thi'sfis dueto-the co 7 operation of the described sound subdui'ng char acteristics of the platen, with'the-aforesaidelas- 40 tic rubber packing vagainst which the type bar, strikes. This packing serves as a sound-damp ener, andthesound-subduing platen also serves as a sound-dampener. 'I'h e-sound-vibration s rei I therefore controlled by the two sound-dampehers,

one of them contacting with the type-bar at its type-end, and the other being in contact; at the sametime with the type-bar at a pointnearita pivot. V The platen, although weighted, is withinthe limit of Weight; which can be satisfactorilyi mounted 'uponfthe' speeding typewriter-carriage The aforesaid'organiz'ation is found inpra silent than any machine heretofore developed in the striking type-bar class, as distinguished from the type-pressing class.

Other features and advantages will hereinafter appear.

In the accompanying drawing,

Figure l is a part-sectional elevation of a typebar, segment, and paper-carriage of an Underwood portable typewriting machine provided with the present improvements; the parts being shown in normal dimensions.

Figure 2 is a sectional perspective to illustrate the heavy-metal core of the platen, and the hel low head of the core.

Figure 3 is a sectional elevation of the platen, the type-bar, and the segment, showing the type printing upon a work-sheet.

Figure 4 is a sectional elevation, showing the usual type-action, and also showing thetype-bar when it contacts with the resilient cushion when the type is nearing the platen.

Theusual type-keys II] are, mounted upon levers I], fulcrumed at l2 and having pins l3 that work infslots [4 provided upon arms l5 of bellcranks l6, fulcrumed at H. From the bell-cranks extend'rearwardly links 18 to; points IQ of pivotal connection with the type-bars 20, which are fulcrurned at 2! upon a segment 22, and carry types 23. The types strike rearwardly against a platen 24, around which is carried a work-sheet 25.

The slot I4 is inclined downwardly and rearwardly to the end that the leverage of the key It], is made very great at the beginning of its down stroke, whereby the type-bar is started into action gently, thus securing an easy finger-touch. As the key descends, the purchase of the lever l I upon the belli-crank arm 15 is diminished, so that finally the type 23is approaching the platen at highspeed. This speeding up of the type-bar absorbs the momentum of the hand of the operator, so that the key eventually comes to rest without shock. This cushioning of the key-stroke at both beginning and conclusion is essential in this class of machines.

Theidescribed increase in the velocity of the type-bar as it approaches the platen has been found to be detrimental, because the type strikes so sharply against the platen or paperas to produce a highly objectionable concussion.

An object of this invention is tominimize this noise, or, at least, to overcome its objectionable sharpness, and to enable the type to not only print quietly, but also to make a black and clear impression upon the work-sheet. This result can be evolved by taking several steps in the construction of the machine.

One step is to effect a substantial reduction in the speed of the type as it strikes the paper, so that the impact of the type against the paper will be much reduced. The problem at this point involves the reduction of the speed by the use of the herein-described means to a point at which the type delivers what would normally be an impression too weak to efiect the necessary clearness in printing; it being premised that by under-speeding the type at the platen, it may, by taking still other steps, be rendered practicable to control the'noise of the impact.

The checking of thc speeding type-bar is effected by a yielding stop 26, which is a segment of a rubber compound such as is generally made up for use as packing; this compound being flexible and resilient, and much more solid than a common soft-rubber band, and being substantially wear-proof so that it is not cut by the edges of the type-bars striking thereagainst This segment 26 is sunken between upper and lower ledges 21, 28, formed upon the front face of a metal segment-plate 29, which may be cast of aluminum or iron. The thickness of the packing is substantially of an inch, and the face of it is substantially of an inch wide. When the type-bar strikes the pad 26, the speeding type-bar is about or g of an inch from the platen. The high resistance offered by the pad 26 checks the speed of the type-bar and type; the type-bar sinking into the pad as seen at 30, Figure 3, and. the speed of the type being suddenly very much reduced below normal, so that the type does not strike quite hard enough to make a satisfactory impression under ordinary conditions. i

The platen itself is one of the interdependent elemfints, the invention enabling the lightlystriking type-bar to produce a satisfactory clearly inked impression upon the work-sheet, and enabling this impression to be made soundsubduing moa s.

For. the platen thereis used a wear-resisting cylindrical jacket 3|, which may be made of the usual rubber compound. It is preferred to make this compound from rubber, carbon-black, whiting, sulphur and zinc. The jacket has a density of 87 to 90, as determined by a densimeter. This jacket is supported by a heavily weighted softrubber core 32 of great bulk. This core is soft and resilient and is made of a compound of rubber, magnesia, whiting, palm-oil, sulphur and paraflin, and has a density of 55 to 60.

This soft-rubber supporting body 32 is molded upon a core 33, which is a length of heavy-iron gas-pipe, and is not only non-resonant, but also affords a rigid support for the cylindrical body 32 and the jacket 3j throughout their length. The body or cylinder 32 is molded upon the metal core, then ground to size; then cementis applied to its periphery, andthe jacket 3| is then forced upon said body. The jacket may also be poured in a mold around said body 32.

At Figure 1, the. platen has the usual length, some lqinches. The diameter of the platen 'is 1 inches, For the purpose of the invention, it haslbeen found that the following dimensions are satisfactory for a platen 1 inches in diameter. The thickness of. the wearing jacket 3! is of an inch The. thickness of the weighted softrubber core 3 2 is of an inch; its outside diameter being 1%, and its central perforation being about These proportions give proper weight to'the axle 33 which may be inch pipe size having a bore of about fi of an inch, and to the cylindrical body 320 f the platen, and, by reason of this weight of the platen, the slowly moving type is enabled to make a bright and clearly inked impression through the ribbon 3 lupon the worksheet 25; while the noise of the lightly-striking type is almost eliminated, by the co-operation of the soft sound-deadening core of the platen 24 withthe resilient rubber-packing 26 into which the type-bar sinks. The platen is from 40 to 50 per cent. heavier than a standard regulation platen of the same over-all dimensions. It will be seen thatby this co-operation the vibration of the type-ban is subdued at two places, one place at 26 and; the other where the type contacts with the ,sound-subduing platen.

'I'heplaten ismounted in end plates 35, 36 of a carriage by means of a le' 31, 38, and is provided with a releasable line-space wheel 39. Endwise movement of a left-hand platen-knob 40 releases the platenfrorn the control of the lineagainst a disk 43, which is fixed upon a hollow stub-shaft 44. In the Figure l'position, a cam 45, upon the axle 31, spreads apart the levers 4i and clamps 42 against .the line-space'wheel 39, holding the latter to the head-disk 43. The levers are mounted upon the head 44, which is slotted to receive the levers 4i, and said head is fitted in a shell 45, which at one end extends within the platen and at the other end extends out from the platen, the shell being tapered at its inner end at 4'! anderigidly. secured. upon a neck 48 formed upon the left-hand end of the tubular axle 33. The inner axle is flattened at 49, whereby it is splined to the tubular axle, a plug 50 having an oblong bore 5! fitting the spline 49, being fastened by screw 52 in the right-hand end of the hollow axle 33, as shown in pending application 548,863, filed July 6, 1931 (now Patent No. 1,931,064, dated Oct. 17, 1933). By releasing screws 52, 53, the platen may be detached from the platen-frame; the axle 38 being first withdrawn and then'the axle 3'! being pressed inwardly to clear it from the carriage-frame end 35. H

When it is desired to set the machine for heavy manifolding, the platen may be adjusted forwardly at each end by means of device disclosed in Patent 1,870,001 granted to me. The carriage runs upon a track-frame 54 by means of a bearing-ball 55, and the track-frame is mounted upon upper and lower links 55 and El, the upper link being formed in two parts which permit a relative endwise adjustment. An eccentric 68 is turned to lengthen or shorten the link 66, and

then the device is fastened by a screw 6t working in the eccentric 58. The links are connected at their forward ends at 69, 10 to the carriage-track frame 54, and at their rear'ends are hinged at ll, 12, to the framework, and hence lengthening the links 66 will adjust the platen bodily forwardly.

and enable the types to print with sufficient force for manifolding.

The weighted soft-rubber cylinder 32 is preferably vulcanized to the iron pipe 33. At its end, the cylinder may have a counterbore to receive the cup 46, which may be riveted or welded upon the end of pipe 33. The head 44 fits into the outer end of the cup, and is secured thereto by a screw 13. The cup 46 serves as an enlargement of tube 33, and there is no metal connection between the wear-resisting jacket 3| and the carriage-frame; said jacket 35 being supported only by the softrubber cylinder, which is non-resonant, and the counterbore in the end of the rubber cylinder fitting the cup, which therefore yieldably supports the end of the rubber platen. This cup is mainly outside of the printing field of the platen and tapers at its inner portion, to afford room for sufficient of the soft-rubber cylinder 32 to serve the described purpose.

Variations may be resorted to within the scope of the invention, and portions of'the improvements may be used without others.

Having thus described my invention, I claim:

1. A typewriter-platen having a wear-resisting jacket which is compounded of rubber, carbon-black, whiting, sulphur and zinc, and having a density of about 87 to 90, and filled by a weighted soft-rubber cylinder compounded of rubber, magnesia, whiting, palm-oil, sulphur and parafiin, and having a density of 55 to 60, and a metal core.

2. A typewriter-platen having a wear-resisting jacket which is compounded of rubber, carrubber, magnesia, whiting, palm-oihsulphur and parafiin, 'andhaving a density of 55 to 60, the

thickness of the wearing jacket %'of an inch; outside diameter of the soft-rubber cylinder 1 of an inch, and centralperforation of the same about ofan inch in diameter; and a metal core. 1 r v ,3. A typewriter-platen having a wear-resisting jacket'which is'compounded ocfrubber, carbon-black, whiting, sulphur andzinc, and having a density of about 8'7 to 90, and filled by a weighted soft-rubber cylinder compounded of rubber, magnesia, whiting, palm-oil, sulphur and parafiin, and having a density of 55 to 60, the platen being substantially of the following proportions: diameter of the platen 1 inches; thickness of the wearing jacket of an inch; outside diameter of the soft-rubber cylinder 1%; of an inch, and central perforation of the same about% of an inch in diameter; and a metal core; said core being a soft-iron pipe having a bore of an inch in diameter.

4. In a typewriting machine, the combination with a set of key-operated type-bars, of means for suddenly decreasing the speed of the typebar beginning when the type is close to the platen, said means being in the form of an elastic pad of high-grade rubber-packing which is struck by the type-bar, slowing the type-bar sumciently to minimize the concussion of the type upon the work-sheet, and a cylindrical platen which is overweighted so as to enable the weakly striking type-bar to effect a clear and.

sharp impression upon the work-sheet; the platen being mainly a substantially solid cylinder of weighted soft rubber which is jacketed with a thin wear-resisting cylinder, the soft interior of the platen serving to mufile the sound of the type-blow, and the soft-rubber platen-body cooperating with the soft-rubber type-bar stop to dampen the type-bar vibrations both at its free end and at a point near the type bar pivot, said wear-resisting jacket being a compound of rubber, carbon-black, whiting, sulphur and zinc, and having a density of about 87 to 90, and. said weighted soft-rubber cylinder being a compound of rubber, magnesia, whiting, palm-oil, sulphur and paraifin, and having a density of 55 to 60.

5. In a 'typewriting machine, the combination I with a set of key-operated type-bars,.of means for suddenly decreasing the speed of the typebar beginning when the type is closed to the platen, said means being in the form of an elastic pad of high-grade rubber-packing which is struck by the type-bar, slowing the type-bar sulficiently to minimize the concussion of the type upon the work-sheet, and a cylindricalplaten which is overweighted so as to enable the weakly striking type-bar to effect a clear and sharp impression upon the work-sheet; the platen being mainly a substantially solid cylinder of weighted soft rubber which is jacketed with a thin wear-resisting cylinder, the soft interior of the platen serving to mufiie the sound of the typeblow, and the soft-rubber platen-body co-operating with the soft-rubber type-bar stop .to dampen the type-bar vibrations both at its freeend and.

bon black, whiting, "sulphur and zinc, and having a density of about 81-to 90, and filled by a' Weighted soft-rubber cylinder compounded of at a point near the type-bar pivot, said wearresisting jacket being a compound of rubber, carbon-black, whiting, sulphur and zinc, and

having: a density. of about ,87; to.9Q, andsaid weightedglsoft-rrubber cylinder being a compound of; rubber, magnesia, whiting, palm-oil, sulphur and paraffin, and, having a density of 55 to 60; the part being of the following proportions: diameter of i the platen 1 inches; thickness of the wearing jacket of aninch; and the thickness of the wall of, the soft-rubber cylinder 5% of magnesia, whiting, palm-oil, sulphur and; parafiin; and having a densityof v55 to 60, the platen being substantially of the following proportions: diameter of the platen 1 inches; thickness of the Wearing jacket of an inch; outside diameter of the soft-rubber. cylinder 1 of an inch, and central perforation of the same about of an inch in diameter; and a metal core; said cylinder being mounted upon a soft-iron pipe having a bore of 'i' of an inch diameter, expanded at one 10 end to form a. hollow head for containing a platen-releasing mechanism.

WILLIAM A. DOBSON. 

